Lest we confuse this with the very useful "crawl ratio" doctrine for anticipating low speed manners in traffic with standard transmission: "The 1st gear ratio times the axle ratio should be above 10 for best results". Example: 2.20:1 close-ratio Muncie with 3.08 axle = misery at 6.8, the 2.52:1 box is preferred here. The 2.95:1 T5 box works well with anything above 3.23.
How does this compare with the auto trans numbers? They all look too low? The missing factor: 1. stall speed means the engine never lugs. 2. the converter's 2:1 (more or less) torque multiplication adds mechanical advantage during roll out.